Biographies of Winston Churchill -- and there are hundreds -- range from extra-short to interminably long. Sir John Keegan's concise take comes in at 176 pages, while Martin Gilbert's official version runs in neighborhood of eight volumes. The late William Manchester's "The Last Lion," comprising three stout volumes, falls somewhere in the middle. Its 3,000 total pages are not unreasonably long, given Churchill's remarkable longevity, which took him from cavalry charges as a young man well into the nuclear age.

"Winston Spencer Churchill, Defender of the Realm, 1940-1965" is the culminating volume of Manchester's trilogy. Manchester, who died in 2004, gets top billing, but the book is very much the work of Paul Reid, who took over writing duties when Manchester fell ill. Reid, a former feature writer for the Palm Beach Post, had no formal historical training, which makes his achievement all the more stunning. This is surely the best installment of the lot.

Reid doesn't get too intoxicated by the Churchillian spell, and gives us a measured portrait of one of the 20th century's most revered statesmen. Reid devotes more than 800 pages to the Second World War. It's a good thing Churchill was blessed with the gift of gab, because he had little to offer his people in the way of victories. The Royal Air Force, of course, performed splendidly in the skies, fending off the Luftwaffe, but British ground forces fared poorly in the war's early years. Churchill had a mania for diversionary thrusts and quixotic campaigns that consigned thousands of men to their deaths. (Gen. Alan Brooke, military chief of staff, said Churchill had 10 ideas every day, one good and nine bad.) Yet the prime minister could spin a fiasco like Dunkirk -- when surrounded British troops had to evacuate northern France by sea -- into a crowning achievement of the British fighting spirit.

The Churchillian record has been tinkered with over the years -- not every biographer comes to praise the blustery, cigar-chomping old man. A revisionary devil could argue that Churchill was a failure as a warlord. Reid doesn't do too much tinkering here, though he does take on the question of his subject's mental health. Churchill was certainly given to gloom and had his share of hang-ups (he detested whistling, for example, and banned it in government corridors). But did he, in fact, suffer from depression, as several biographers have contended? Reid concludes otherwise: "Nothing -- not his moods, not Britain's defeats, not the slow strangulation of the U-boat blockade, not his reluctant generals -- impeded Churchill's capacity to inspire his countrymen and to fight for their salvation. Nothing diminished his love for his family. Nothing undercut his love of life. If one accepts Freud's dictum that mental health is the ability to love and work, Churchill possessed his full mental health."

Elsewhere, Reid composes memorable descriptions of Churchill that conjure up the man in a sentence: "Churchill arrived on the scene like a summer squall at a sailboat regatta." An angry Churchill "was drumming his fingers on the table, and his lower lip jutted out like the prow of a dreadnought." Reid also paints vivid and horrific sketches of bombed-out London, including a direct hit on a tube station: "More than 250 Londoners drowned in the deluge of sewage and water or were crushed by debris, including a double-decker bus." But the vast narrative demands a steady commitment from the reader; there is such a steady march of detail here, and countless spicy quotes drawn from diaries and memoirs, that Reid's jaunty pace can slow to a slog.

Britain emerged on the winning side bankrupt and beholden to the United States. Churchill was thrown out of office in 1945; he misread the mood of the country. Churchill infamously compared the tactics of the Labor party to the Gestapo. "I'll tear their bleeding entrails out of them," the bellicose Churchill said of his political opponents. Given Reid's treatment of the war, his sections on Churchill's last decades -- he served one more term as prime minster from 1951 to 1955 -- seem cursory. Still, Reid has written a win- ning, full-blooded biography.